Well, Terror of the Zygons is coming out on DVD in September, and is the last Tom Baker story remaining to be released in that format. But yeah, these videos seem a bit much just for that.
A complete DVD set crossed my mind too, but that would be MASSIVE. Maybe some kind of digital release? Or a special documentary retrospective?
And yes, there will be Zygons in the 50th Anniversary special. So maybe something to do with that?